Linking large-scale circulation patterns to the distribution of cold water corals along the eastern Rockall Bank (northeast Atlantic)

Cold-water corals (CWC) are known to tolerate a relatively wide range of environmental conditions. However,
along the basin margins of the Rockall Trough (NE Atlantic), the habitat of CWC is confined to a narrow
range of 525–1200 m water depth, and the reason for that is not fully understood. To investigate the
distribution of CWCs in this area, current velocities and water mass distribution in the Logachev Mound
Province were measured with two long-term (1 year) moorings equipped with an acoustic doppler current
profiler and fluorescence+turbidity sensors. Additional ship-based water column profiles and discrete water
samples, covering a full diurnal tidal cycle, were taken for chemical parameters. The results indicate the
presence of a boundary current along the eastern flank of the Rockall Bank, that transports a nutrient-rich water
mass southwards and governs the direction of particle transport at the depth band of the CWC mounds. Based
on literature results, this northern water mass is identified as Wyville Thomson Ridge Overflow Water (WTOW).
The density envelope and depth distribution of WTOW match the reported occurrence of CWC mounds in the
Rockall Trough. Hence, the presence of WTOW may be a necessary condition for coral growth and therefore
mound formation in the Rockall Trough, e.g. by forming a conduit for particles and coral larvae.